Nickel alloys

ABSTRACT

A corrosion resistant precision casting alloy particularly suitable for use as a dental alloy comprises essentially, by weight, at least 60 percent nickel, 10 to 25 percent chromium, up to 10 percent molybdenum, 0.50 to 1.5 percent manganese, up to 6.5 percent tin, 1.0 to 7.5 percent gallium, up to 5 percent copper, up to 4 percent silicon, up to 2.0 percent aluminum, up to 5 percent cobalt and up to 0.2 percent carbon, the combined total amount of tin and gallium not exceeding 7.5 percent.

United States Patent [1 1 Dudek et al. 0

[451 Sept. 23, 1975 1.54] NICKEL ALLOYS 175] Inventors: Ronald P. Dudek, River Grove;

Peter Kosmos, Alsip: John A. Tesk, Wood-Ridge, all of 111.

[73] Assignee: Howmedica, lnc., Chicago, 111.

[22] Filed: Sept. 26, 1974 21 Appl. No.: 509,557

Related US. Application Data [63] Continuation-impart of Ser. No. 317,594, Dec. 22,

1972, Pat. No. 3,841,868.

[52] US. Cl. 75/171 [51] Int. Cl. C22C 19/05 [58] Field of Search 75/171, 170; 148/32, 32.5

[56] References Cited UNITED STATES PATENTS 2,226,079 12/1940 Spanner 75/172 2,460,595 2/1949 Reich 75/134 3,134,671 5/1964 Prosen 75/172 Nielsen et a1. 75/165 Primary Examiner-R. Dean Attorney, Agent, or Firm-Pennie & Edmonds [57] ABSTRACT A corrosion resistant precision casting alloy particularly suitable for use as a dental alloy comprises essentially, by weight, at least 60 percent nickel, 10 to 25 percent chromium, up to 10 percent molybdenum, 0.50 to 1.5 percent manganese, up to 6.5 percent tin, 1.0 to 7.5 percent gallium, up to 5 percent copper. up to 4 percent silicon, up to 2.0 percent aluminum, up to 5 percent cobalt and up to 0.2 percent carbon. the combined total amount of tin and gallium not exceeding 7.5 percent.

7 Claims, N0 Drawings 1 NICKEL ALLOYS RELATED APPLICATION This application is a continuation-impart of applicants copending application Ser. No. 317,594, filed Dec. 22, 1972 entitledFNickel Alloy, now U.S. Pat. No. 3,841,868.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to corrosion resistant precision casting alloys particularly suitable for use as dental alloys. I

2. Prior Art g Metals and metal alloys are used extensively in restorative and corrective dentistry for removable restorations, inlays, crowns, and bridges, orthodontic applicances, and the like. Dental alloys must meet stringent physical and chemical requirements. First, the chemical nature of the alloy must be such that no harmful physiological effects are produced on the patient or the operator. The alloy must be stainless and resistant to attack by the various acid and alkaline substances naturally present in the mouth and in foods and beverages. It must be capable of being fabricated into the desired dental appliances by dentists and technicians and yet must be hard enough and strong enough to resist wear and deformation in use, and it must be capable of being cast to form precision castings free of inclusions, blow holes and other defects.

Gold alloys were originally the most widely used and useful of the dental alloys. However, the high cost and scarcity of gold led to the development of dental alloys comprising predominantly cobalt and chromium with minor amounts of tungsten, nickel and other metals. These cobalt-chromium base dental alloys are exemplified by those disclosed in U.S. Pat. Nos. 1,961,626 and 2,134,423 to Enrique G. Touceda. More recent work has led to the development of dental alloys comprising predominantly nickel and chromium with minor amounts of molybdenum, iron, copper and other metals. These newer nickel-chromium base dental alloys are exemplified by the alloy disclosed in U.S. Pat. No. 2,597,495 to Jackson and Simmons. All of these prior dental alloys possess to a greater or lesser extent the characteristics required of such alloys as previously discussed. However, none possesses all of the required characteristics to the optimum extent, and research and development of new dental alloys with improved characteristics is constantly taking palce.

In our copending application Ser. No. 317,594 we have described an improved corrosion resistant alloy that comprises essentially, by weight, 15.0 to 25 percent chromium, 3.0 to 6.0 percent molybdenum, 1.0 to 4.0 percent tin, 0.5 to 1.5 percent manganese, 0.5 to 5.0 percent copper, 1.0 to 4.0 percent silicon, up to 1.0 percent aluminum, up to 1.0 percent cobalt, up to 0.2 percent carbon and the balance (52.3 to 79.0 percent) nickel. The resulting alloy is capable of being cast to form precision castings that are free of inclusion, blow holes and other defects, and the alloy is relatively easy to work while possessing adequate strength and hardness.

The aforesaid alloy contains a small but significant amount of tin which greatly improves the fluidity of the molten alloy and also contributes to the strength and hardness of the cast alloy without unduly reducing the elongation of the alloy. As a result of further investigations with respect to this and related alloys we have found that gallium imparts essentially the same characteristics to the molten and cast alloy as tin and may be included in the alloy along with tin or in place of tin to obtain an alloy having excellent casting properties and that.is relatively easy to work while possessing adequate strength and hardness. In addition, we have found that the amount of tin and/or gallium included in the alloy may be significantly increased over the amount employed in the alloy of our copending application and further that the alloy can optionally contain significant amounts of copper, silicon, aluminum and cobalt.

SUMMARY OF THE INVENTION The improved corrosion resistant alloy of the inven tion comprises essentially, by weight, at least nickel, 10 to 25% chromium, up to 10% molybdenum, 0.50 to 1.50% manganese, up to 6.5% tin,.=l.0 to 7.5% gallium, up to;5% copper, up to 4.0% silicon, up to 2.0% aluminum, up to 5% cobalt and up to 0.2% carbon, the combined total amount of tin and gallium not exceeding 7.5%. The resulting alloy is capable of being cast to form precision castings that are free of inclusions, blow holes and other defects, and the alloy'is relatively easy to work while possessing adequate strength and hardness.

DESCRIPTION or PREFERRED EMBODIMENT is employed for its inherent resistance to corrosion.

Chromium, the other predominant component of the basic alloy composition, enhances the corrosion resistance of the alloy and also is a solid solution/precipita tion hardener. In addition, a small but significant amount of manganese acts as a safeguard against possible sulfur contamination and a small amount of molybdenum is advantageously employed to enhance the corrosion resistance of the alloy and as a powerful solid solution/precipitation hardener. Optionally, the alloy may contain a small amount of silicon that acts as a deoxidizer and also lowers the fusion temperature of the alloy, and a small amount of copper may be added to improve the surface finish of the cast alloy. Small amounts of cobalt and aluminum, the latter as a deoxidizer and precipitation hardener, and a very small amount of carbonmay also be present in the alloy. Lastly, the alloy of the invention contains a small but significant amount of gallium with or without a small amount of tin which greatly improves the fluidity of the cellent casting properties and that is relatively easy to work while possessing adequate strength and hardness. In addition we have found that the amount of tin and gallium included in the alloy may be significantly increased over the amount employed in the alloy of our copending application Ser. No. 317,594, and further that the alloy can optionally contain significant amounts of copper, silicon, aluminum, cobalt and molybdenum, as hereinafter described.

The relative proportions of the various elements comprising the new alloy composition has been determined as the result of an intensive investigation to obtain an alloy having optimum chemical and physical properties. Specifically, we have found that the alloy composition of the invention should contain at least 60 percent by weight nickel, from 10 to 25 percent by weight chromium, up to 10 percent by weight molybdenum, from 0.50 to 1.5 percent by weight manganese, from L0 to 7.5 percent by weight gallium, up to 6.5 percent by weight tin, up to 5 percent by weight copper, up to 4.0 percent silicon, up to 2.0 percent by weight aluminum, up to 5 percent by weight cobalt and up to 0.2 percent by weight carbon. The combined total amount of gallium and tin should not exceed about 7.5 percent by weight of the composition. Moreover, it should be noted that molybdenum, tin, copper, silicon. aluminum, cobalt, and carbon are optional constituents of the alloy composition, and further that gallium is an essential constituent thereof. A corrosion resistant alloy which contains the aforementioned components in the amounts specified may be readily cast to produce precision castings that may be easily finished and that have the necessary strength and hardness for the applications intended. in particular. the presence of gallium and tin in the alloy composition effects a significant improvement in these essential characteristics.

The following specific examples describe the preparation of preferred alloy compositions of the invention.

EXAMPLE I A base alloy composition comprising 68.25 parts by weight nickel. 20.0 parts by weight chromium. 4.5 parts by weight molybdenum and 1.25 parts by weight manganese was prepared by melting the substantially pure components in a crucible 1.5 parts by weight copper, 2.5 parts by weight silicon and. most important, 2.0 parts by weight tin were then added to the alloy melt. After the molten ingredients were thoroughly mixed to form a homogenous melt. the molten alloy was cast into a mold or investment of refractory material to obtain a cast metal shape. Several such investment castings were made. In each case the resulting cast metal shape conformed precisely to the shape of the investment mold and was without blow holes, inclusions or other defects'The alloy shape that was allowed to air-cool in its investment mold had a Rockwell B hardness of 83.

and 0.2 percent yield strength of 49,500 psi and a maxiutes after which the alloy was quenched in water. The generally good working characteristics typical of the alloy when air cooled can therefore be improved by the two aforementioned techniques or similar treatments following casting. All of these physical characteristics reflect a substantial improvement over the properties of similar, but tin-free, corrosion resistant precision casting alloys known in the prior art.

EXAMPLE II Composition by weight) and properties Ni 68.25 Si 2.50 Cr 20.00 Cu 1.50 Mo 4.50 Sn l .00

I Mn 1.25 Ga 1.00

Proportional limit (psi) 31,600 0.2% Yield Strength (psi) 42.600 Ultimate Tensile Strength (psi) 661,300 Elongation (/1 l l Rockwell 8" Hardness X2 EXAMPLE Ill The alloy composition of Example I was modified by the substitution of 2 percent by weight of gallium for the 2 percent by weight of tin present in the alloy to obtain a corrosion resistant dental alloy having the composition listed below. The molten alloy was cast into investment cast shapes to provide test specimens free from defects and having the physical characteristics also listed below.

Composition ()i by weight) and properties Ni 68.25 Si 2.50 Cr 20.00 Cu |.50 Mo 4.50 Ga 2.00 Mn 1.25

Proportional limit (psi) 44,700 0.2% Yield Strengthtpsi) 51,500 Ultimate Tensile Strength (psi) 79,000 Elongation (f z) H Rockwell 8" Hardness 8] EXAMPLE lV An alloy having the composition listed below was prepared in accordance with the procedure described in the Example I, and test specimens were prepared by investment casting of the alloy to obtain defect-free cast alloy shapes having the physical characteristics also listed below.

Composition (5% by weightyarid properties Ni Cr Cu l . -Continued -Continued Composition (/fby weight) and properties An alloy having the composition listed below was prepared in accordance with the procedure described in the Example I, and test specimens were prepared by investment casting of thealloy to obtain defect-free cast alloy shapes having the physical characteristics also listed below.

Mo 4.50 Y Sn 3.0 Mn 05 Ga 7.5 Mn 1.25 Ga 1.0 5

, Proportional Limit (psi) 35.000 Pr rti al Li i i 38 6()0 0.20 Yield Strength (psi) 42,500 02% Yield Strength (psi) 47.500 Ultimate Tensile Strength (psi) 69.000 Ultimate Tensile Strength (psi) 69,800 Elollgiltilm (Z) l6 Elongation (71) 6 Rockwell "8 Hardness 72 Rockwell "B" Hardness 87 lo EXAMPLE Vlll EXAMPLEV The fore om allo com osttions were modified b g g y P k y v y b alloy havmg cofnposltlon hsted below s the inclusion of up to 10 percent by weight molybdeprepared in accordance with the procedure described um, up to 9 percent by weight f tin and 7 5 percent f" the Example l1 and Specimens wer'e Prepared by by weight of gallium, up to.5 percent by weight copper, investment casting of the alloy to obtatn defect-free up to percent by weight silicon up to 2 percent cast alloy shapes having the physical characteristics by weight aluminum and up to 5 percent by i h also listed belowbalt. All possessed the improved physical properties characteristic of the alloy composition of the invention.

We claim: Composition 1 by weight) and pmpenies l. A corrosion resistant hot workable and hardenable precision casting alloy consisting essentially, by weight: Ni 66.25 Si 2.5 Cr 20.00 Cu 1.5 Mo 4.50 Sn 2.0 Mn 1.25 Ga 2.0

Nickel at least 607: Proportional Limit (psi) 37.000 Chromium 10 2571 0.271 Yield Strength (psi) 47.400 Molybdenum 0 l071 Ultimate Tensile Strength (psi) 7 73,600 Manganese 0.50 1.50 Elongation (9. ll. Tin 0 6.5 Rockwell B" Hardness 86 Gallium I 1.0 7.5

Copper 0 4 5.0 Silicon 0 4.0 Aluminum 0 2.0 Cobalt 0 5.0 EXAMPLE Carbon 0 02 An alloy having the composition listed below was prepared in accordance with the procedure described the combmed total amount M and gallium not in the Example I, and test specimens were prepared by ceedng investment casting of the alloy to obtain defect-free The COTYOSIO" 3515mm alloyvaccmdmg 10 claim 1 cast alloy shapes having the physical characteristics 40 conslstmg essemlauy y Welght: also listed below.

Nickel 68.25% Chromium 20.0%

- Molybdenum 4.5% Composition (7: by weight) and properties Manganese L357 Gallium 2.0% Ni 66.25 Si 25 Copper 1.5% Cr 20.00 Cu l .5 Silicon 2.5% I Mo 4.50 Sn l.0 Carbon Less than 0.0W1. Mn L25 Ga 3.0

p i l Limit (psi) 37'200 3. The corrosion resistant alloy according to claim 1 03% Yield Strength (Psi). 46700 consisting essentially, by weight: Ultimate Tensile Strength (psi) 68,700 Elongation (7:) 9 Rockwell B Hardness 86 Nickel 75.5% a Chromium 15.0'7:

. Manganese I 0.571 Gallium 7.57 EXAMPLE v11 Copper 1.571

Carbon 0.01%.

. less than 4. The corrosion resistantalloy according to claim 1 consisting essentially, by weight: 

1. A CORROSION RESISTANT HOT WORKABLE AND HARDENABLE PRECISION CASTING ALLOY CONSISTING ESSENTIALLY, BY WEIGHT:
 2. The corrosion resistant alloy according to claim 1 consisting essentially by weight:
 3. The corrosion resistant alloy according to claim 1 consisting essentially, by weight:
 4. The corrosion resistant alloy according to claim 1 consisting essentially, by weight:
 5. The corrosion resistant alloy according to claim 1 consisting essentially, by weight:
 6. The corrosion resistant alloy according to claim 1 consisting essentially, by weight:
 7. The corrosion resistant alloy according to claim 1 consisting essentially, by weight: 